The present invention is related with the techniques for flushing cisterns, and more particularly, it is related to a siphon flush apparatus.
As it is widely known, several types of flushing devices have been used for many years in order to flush cisterns of toilettes.
Nevertheless, the main problem in almost all of the flushing devices that are known up to date is leakage. Some of the recent developments intended to give the best performance in flushing operations by incorporating the siphon principle to start the water discharge from the cistern into the toilet bowl for its cleaning.
One example of the above is U.S. Pat. No. 3,851,338, which describes a flushing device for toilets where a siphon empties a flush tank and becomes inactive until the tank is full and flushed again. The system includes a float that is slidably mounted in a chamber so that when the float is forced down for flushing, water is forced from the float chamber into a siphon, either alone or with water from an inlet valve, to start the siphon action to empty the flush tank. When the float is forced down, the water inlet valve is opened to supply additional water to start the siphon. Then the inlet valve remains open until the tank is refilled.
The invention described above presents the inconvenience of needing means for preventing a reverse flow from the tank into the inlet pipe when a failure in the water supply occurs. In addition to the fact that the formation of the siphon needs a complex construction in regard to both, elements and space.
As it will be shown by the analysis of the prior art, the main differences between the known devices that use a siphon for flushing is the method by which the siphon is formed, which at the end allows a better performance when flushing.
Another example of siphon construction is U.S. Pat. No. 4,024,589. This patent discloses a flush valve of siphon type with a supply jet feeding into the up-leg and having a flap-float valve which is responsive to water level and serves to divert the supply flow to refill the tank after completion of the flushing action. In the preferred embodiment, the float of the float-flap valve is disposed in a chamber that insures that it will operate only after full completion of the flushing action.
The invention described above is a combination of a float flap valve directly put in the inlet water, as well known in the prior art, and a siphon with a jet stream to initiate the siphonic effect. However, it has the inconvenience of having a complex design that makes it difficult to give maintenance and keep fit. Moreover, its performance depends, in a great extent, on the effectiveness of the flap-float valve, which in turn can be easily susceptible to leakage.
Similarly, British patent No. 2041421 describes another siphon unit for flushing cisterns that has a flushing piston as well as a xe2x80x9cUxe2x80x9d shaped construction. One arm of the siphon tube forms an inlet for communication with the cistern to fill said arm to a level corresponding to the level of liquid in the cistern. The other arm, which forms the outlet, allows discharge for flushing. The main inconvenience of this system is the needing of a piston inside a chamber that is formed at the inlet. Therefore, it is needed a very good sealing at the piston and a considerable force to push the water and form the siphon. In addition, maintenance of the apparatus is very complicated.
Another xe2x80x9cUxe2x80x9d shaped siphon apparatus is described in U.S. Pat. No. 4,268,924, having a similar construction to that described in last paragraph but having some differences at the valve for forcing water to enter into the system.
Other kind of siphon assembly for flushing cisterns is described in British patent No. 2167778, wherein a siphon assembly comprises two parts. The first part includes a down leg of the siphon duct, which lower end is mounted in the cistern base; and, the second part includes the up-leg and the inlet chamber in which the flushing piston is received. The parts are releasably connected by a push fit spigot and a socket joint that is secured by a removable pin received transversely through location formations on each part near the top of the legs, further formations located near the bottoms of the legs being received in vertical sliding relationship.
The latter invention has yet the inconvenience of needing a flushing piston to initiate the siphoning operation, besides of having a complex assembly.
Another kind of system to form the siphon is shown in European Patent No. EP0209477, which presents a flushing device having a floating siphon bell for flushing tanks that include an external tubular casing and the floating siphon bell inside. This system needs a complex valve system, which makes it difficult to maintain as well as expensive.
Another bell shaped siphon is that described in European Patent No. 0302150, which describes a siphon having an inverted flow-directing element positioned over a down pipe. At the lower end of the bell, valve means are fixed in relation to the down pipe. By depressing the bell, a siphonic action is initiated which flushes the cistern. In order to start the siphon, it is also needed the equivalent of the piston of other inventions, since this bell includes a diaphragm, which functions as a check valve that allows the water to enter into the bell when it is used. Such water is forced by the diaphragm into a restriction of the bell when the bell is pushed down, thus forming the siphon. In this case, the formation of the siphon is highly dependent on the diaphragm performance. Furthermore, the restriction necessary to form the siphon is very severe, so that a very high pressure drop is caused, which results in a deficient flush of the toilet since the flow area at the down pipe is greater than the flow area at the upper part of the bell.
In addition, the discharge tube should be over the water level. Although this prevents water leakage effectively when the flush is not being used, it is also the cause of needing the flow restriction and the diaphragm at the bell for allowing the formation of the siphon.
Having in mind the drawbacks of the prior art, it is an object of the present invention to provide a siphon flush apparatus, which does not need a jet stream of water to initiate the siphonic effect.
Another object of the present invention is to provide a siphon flush apparatus, which does not need a piston to initiate the siphonic process.
One other object of the present invention is to provide a siphon flush apparatus which does not need any valve means to initiate the siphonic process.
It is yet another object of the present invention to provide a siphon flush apparatus, which can remain without any leakage into the flushing tube.
An additional object of the present invention is to provide a siphon flush apparatus having a simple construction such that the maintenance thereof be cheap and easy.